Radar-command system of time coded pulses



6 Sheets-Sheet 1 April 18, 196] J. J. HAGOPIAN ETAL RADAR-COMMAND SYSTEM OF TIME CODED PULSES Filed March 19, 1948 A @miw 1 TAIR@ April 18, 1961 J. J. HAGoPlAN ETAL 2,980,903

RADAR-COMMAND SYSTEM oF TIME CoDED PuLsEs Filed March 19, 1948 6 Sheets-Sheet 3 l I l Fna/v Ram/IR @all 30o/as Gin- (/3) /aK.c. asc. (/6/I l I I I l l I I I dIll;

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(Conf/1? wm/fromfs) BY olfg/S G- mfg CIM ATTORNEY April 18, 1961 .1.J. HAGOPIAN ETAL 2,980,903

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April 18, 1961 J. J. HAGOPIAN ETAL 2,980,903

RADAR-COMMAND SYSTEM oF TIME CoDED PULsEs Filed March 19, 1948 6 Sheets-Sheet 5 I I Q' DI BLac/rm/a asc/LL. (48) L fo/us GATE [49) CO//V- OUTPUT 65'0) 25o/as @Ars (50 40o/us @arf frz) L 20 Kc. asc/Mm my L I conv. i"/ (697 L conv. *2 {s} L co/lv. *.3 (69) cof/v. "if (70) 409:15 GATE {g4} Ffm co/Mammsg L Ecc: f s-Jaml/vfszj L l e I l l 1ra-*i i l i INI/ENT ORS J EL aca d ago/wan ATTORNEY April 18,1961

Filed March 19, 1948' J. J. HAGOPIAN ET AL RADAR-COMMAND SYSTEM OF TIME CODED PULSES PHL SE' 6 Sheets-Sheet 6 POS/T/I/E PULSE C. UI/TPUT as.

r0.0. INPUT JNVENTIOR. Ja co6 d Haya/Waff l Daag/a5 G. Wega ATTORNEY RADAR-COMMAND SYSTEM F TllVlE CODED PULSES Jacob J. Hagopian, Hollywood, Calif., and Douglas G. Trego, Akron, Ohio, assiguors to Goodyear Aircraft "Corporation, Akron, Ohio, a corporation of Delaware Filed Mar. 19, 1948, ser. No. 15,766 6 claims. v(ci. 34a-7.6)

This invention relates to systems for remotely controlling bodies, such as airplanes, and the like, and, more particularly, is concerned with remote control system combined with radar. f

It is the general object of the invention to provide apparatus which will serve to both follow a body or vehicle by radar, and issue command signals to the body or vehicle to control the movement thereof.

Another object of the invention is to provide apparatus of the indicated type which will also function to locate a target, landing eld, harbor, or the like, for the body or vehicle.

Another object of the invention is the provision of apparatus for use in conjunction with a conventional radar and which will use the time interval between the last desired echo signal and the following search'pulse to transmit intelligence signals to an airplane or other vehicle, first to interrogate the vehicle through apparatus carried by it, and if the vehicle responds to the interrogation -to command the vehicle with control signals such 'as left, rig t, down, or auxiliary.

Another object of the invention is to provide coder apparatus in association with a radar transmitter, the coder being triggered by a radar pulse to modulate the radar wave to send interrogation pulses at selected micro-second time intervals to a decoder carried by the body or vehicle being controlled, and if the decoder opens control channels, the coder will transmit control signals through the decoder to operate one or more controls v carried by the body or vehicle.

Another object of the invention is to provide apparatus of the described character which can be used to follow and control a plurality of bodies simultaneously.

The foregoing objects of the invention, and other objects which will become apparent as the description proceeds, are achieved by incorporating with a radar transmitter an apparatus for transmitting control pulses of different time separation by modulating the radar wave -during the time interval between the last desired echo signal and the following search pulse. paratus is used in conjunction with a decoder carried by the body or vehicle being controlled, the decoder having separate channels responding to the different pulse separations to control the body or vehicle. If several bodies or vehicles are being simultaneously followed and cornfrnanded by the radar, interrogation pulses of different time separation may be sent to the several airplanes, and the decoding apparatus associated with each airplane will vonly respond to the control information sent following the correct interrogation signalto each particular air-` plane.

For a beter understanding of the invention, reference should be had to the accompanying drawing, wherein:

Fig. 1 is a block wiring diagram of apparatus incorporati'n'g the principles of the invention and comprising v'au coding apparatus used to control three separate airfpla'nes with four different controls consisting of right, tslftn dov-Jn. csauxiliaryn;

States Patent Fig. 2 is a diagrammatic showing of signal pulsesused in the apparatus of Fig. l and utilizing a radar Search pulse repetition frequency of four hundred cycles 'per second or twenty-ve hundred micro-seconds per cycle, vwhich is adequate for a hundred mile search range;

Fig. 3 diagrammatically illustrates -pulse times and wave forms in the coder apparatus illustrated inFig. l;

Fig. 4 is a block Wiring diagram illustration of the decoding apparatus associated with each body being guided;

Fig. 5 is a diagrammatic illustration of pulse times and y wave forms in the decoder apparatus of Fig. 4;

The aforesaid ap- Fig. 6 is a schematic wiring diagram kof the "le'ft and right signal. control circuits shown in block diagram form in Fig. 4;

Fig. 7 is Va schematic wiring diagram of the.down" signal control circuit shown in block diagram form in Fig. 4.

GENERAL DESCRIPTION lt will be understood that the apparatus of the present invention is adapted to be used to control any of a wide variety of objects, the radar and coder may be carried in an airplane or other vehicle or on the ground, and the distances through which the apparatus functions ymay be as desired, subject to the limitations of the radar equipment. However, the apparatus is primarily designed to control one or more airplane or missiles from a mother airplane and up to distances of one hundred miles, and for purposes of simplification will be hereinafter so described. A

As heretofore noted, the coder apparatus of Fig." `1 is adapted to be associated with a radar transmitter, yand the decoder *apparatus of Fig. 4 is adapted to be carried on the airplane which is being followed and controlled by the radar. The coder apparatus is used to modulate and control the transmission of micro-second pulses von the radar during the period between the last desired echo signal and the following search pulse. With the radar operating upon the basis of four hundred cycles per second, each radar cycle is twenty-live hundred micro-seconds long which is adequate for a one hundred mile search range, and/yet will provide time in each cycle for command pulses.

Fig. 2 illustrates in diagrammatic, time-spacing form the twenty-tive hundred micro-seconds cycle, Without the 'ligure attempting to show the Wave form or the length or shape of the pulses. The first fifteen hundred microseconds of the cycle is utilized to transmit the radar `pulse and get back the last echo of the pulse. This then provided a one-thousand micro-second interval in each radar cycle in which Van individual airplane or airplanes can be interrogated and controlled.

The apparatus has been illustrated and will be described as controlling three airplanes, although it will be understood that more or less airplanes can be controlled. Usually no more than three airplanes are controlled inasmuch as following and controlling more than this number kbecomes ditiicult. It is also to be noted that each controlled airplane ywill have an auto-pilot and a course corrector and the apparatus of the present invention will supplement these only when additional control is desired or necessary. Y

v Specifically, Fig, 2 illustrates the pulse signals transmitted to airplane No. 1 as including` a pair of pulses, each about one-half micro-second long, transmitted at T equals lifteen hundred micro-seconds Vand T equals vfifteen hundred and titty micro-seconds. The decoding apparatus carried yby airplane No. l Will not respond to any control signals unless such control signals follow the `interrogation or trigger signals time-spaced as just described. ln a like manner, the interrogation lsignals se'xt to airplane No. 2 are sent at T equals fifteen hundred and T equals sixteend hundred and iifty micro-seconds. No other combination of interrogation signals will trigger the decoder apparatus carried by airplane; No. 2 for control operation. Similarly, the decoder apparatus of airplane No. 3 will respond only to interrogation signals sent at T equals iifteen hundred and T equals seventeen hundred and iifty, all as illustrated in the indicated wave form. l

It will be understood that associated with the coder apparatus is a hand operated control mechanism which 'will include positions for the selection of an interrogation signal for any one `of the three controlled airplanes. Only one airplane can be interrogated at a time. Such selector buttons or mechanism is indicated diagrammatically in Fig. 1 in vassociation with mixer Nos. l, 2 and 3, of the synchronizing Unit of Fig. l, and has been indicated in the drawing by thenumerals 1, 2 and 3, respectively. 'After a given airplane is selected to be controlled, then the control mechanism can be hand actuated to provide a left, right, down or auxiliary control, such additional control mechanism being indicated diagrammatically in association with mixer Nos. 1, 2, 3, and 4 in the Command Unit portion of the coder apparatus s hown in Fig. l, such additional hand operated controls being indicated respectively by the numerals 4, 5, 6

f and 7. Thus, when checking on airplane No. 1, control entiator, the coincidence circuits, the mixers, the Eccles- Jordan circuit, and the variable gate, are individually well known and understood by the man skilled in the art, but out of an abundance of precaution, individual schematic wiring diagrams of typical circuits for the individual blocks of Fig. lfhave been illustrated in part in Figs. 6 yand, 7, each `o f ,these tlguresvbeing appropriately identified by the title of the block. The particular circuit constants or individual circuit item values in each of Figs. 6 and 7 have not been identified for the reason that `these constants will vary dependent upon the type of tube used, and the relation of the. other circuits. The selection4 of proper constants to achieve the relationship and eiiects 1 will be positioned to interrogate airplane No. 1 and v 1 trigger the decoder apparatus carried thereby. Then, should the radar scope show the plane straying to the left, right control 5 will be pushed to bring the airplane No. l back on course. It is possible to push only one of the controls 4, 5 and 6 at one time, although control 7, auxiliary, can be operated simultaneously with any of the controls 4, S or 6.

It will be understood that the principles of the invention can be utilized to provide other than 1eft, right, down and auxiliary control functions if desired for any particular situation. Usually the left and righ controls are eiected by means of a non-locking three position lever switch having a neutral center position, vand the auxiliary command is selected by a similar switch with one position to select an on-off pulse signal and the other position to select the proportional signal, the magnitude of the latter being determined by a potentiom- 'eter 7 mounted in the control mechanism. The down command is selected by a non-locking push-button fitted with a guard to prevent accidental operation, the control switches usually actuate relays mounted within the coder apparatus in a manner that will be understood.

`It is advisable to transmit a control or command signal for a period of time, such as one complete scan of the radar antenna, to insure that the airplane being controlled is illuminated by the transmitted beam, and for this reason the control relays remain closed after actuation as long as the control is closed, or if the control is pushed -and released for a period of two seconds approximately.

This insures that the radar antenna completes at least A one scanning cycle. Of course, a control signal can be Vactuated for additional periods or scans of the radar antenna any desired number of times. In any event, a single scan of the radar antenna will include several hundred radar cycles each of the 2500 micro-second length, but with only perhaps a small number of the radar cycles occurring while the controlled airplane is actually illuminated by the transmitting radar antenna.

Fig. 2 also illustrates in time relation form the char- ,acter of the command or control signals to each of the airplanes, namely, lef right, down, auxiliary fixed and auxiliary variable.

Coder-general description herein setforth is Within the ability of the man skilled inthe art. h h ,Q h

The interrogation and control signals generated by the coder serve as an input to the modulator of the radar transmitter, identiiied `by the numeral "8, 4and controlfof the modulator during that portion'pof the period between Search t pulses which are not used for receiving radar echoes. In the apparatus of the invention, the coder is an externally triggered unit and requires a monitor trigger pulse from the radar ,at the start of the radar cycle, `speciiically, T equals zero` micro-seconds, in order` to start the coder into operation. rI`he signals from the coder determine only the time spacing between the transmitted pulses, their widthand amplitude being determined by the modulator. t

C0der-nerr0gat0n pulse generator The apparatus of Fig. l is divided by-a dash line into a Command Unit and a synchronizing Unit. The Syn-` chronizing Unit comprises the interrogation pulse generator` which generates (l) the interrogating signals and `(2) fa timing pulse which actuates the command pulse generator. The wave forms occurring at various points of the generator chain are shown in Fig. 3.

The input to the interrogation pulse generator or Synchronizing Unit is obtained from the radar set 8 and consists of a monitor pulse occurring with the start of each radar cycle (T equals zero). The monitor trigger pulse input connections are indicated by the numeral 8DL and the numeral 9. The input Sais applied to the fifteen hundred micro-seconds gate 10 whose output at T equals fifteen hundred micro-seconds is applied to each one of blocks 10, 11 and 12, comprising, respectively, mixer No. 1, mixer No. 2, and mixer No. 3. Also, the output of` gate 10*l is applied to trip a three hundred micro-sccond gate 13 and a one hundred micro-second gate 14. The monitor trigger pulse is also applied by the connec- `tion 9to the Eccles-Jordan circuit 15, as` shown, and nserves to establish the desired initial circuit condition at `the start of eachiirst radar cycle.

The three hundred micro-second gate 13 shock-excites a ten kc. oscillator 16 whose first half cycle of oscillation is negative. The oscillator output (see Fig. 3) contains-thre'e 'cycles and the output wave is squared and diiierentiatedin the circuit 17 to give an output signal of alternately positive and negative pulses spaced fifty microseconds `apartand starting with a negative pulse at T equals ifteen hundred micro-seconds. Of course, the rthree hundred micro-seconds gate controls the duration of the oscillator output, all as will be evident from Fig. 3'.

The one hundred micro-second gate of circuit block 14 is applied to coincidence circuit No. l, block 18, and therein selects the first positive pulse derived from the ten kc. oscillator (T equals fifteen hundred fifty microseconds).` This pulse and the trigger pulse are fedl to mixerNo. Lidentified by the numeral 10, and the positive pulse from the coincidence circuit No. l also trig, gers a one hundred and fifty micro-second gate 19 which starts at T equals lifteen hundred fifty micro-seconds and ends at T equals seventeen hundred micro-seconds. The

ygate 19, applied to coincidence circuit No. 2identie'd the drawingby numeral Zi),l selects` the second` posi.- ttve oscillator pulse (at T equals sixteen' hundred-'nity micro-seconds) whichis fed, along with thetriggerpulse, to'mixer No.2, identified by the numeral 11. The output fcoincidence circuit Nd. 2 also starts a one hundred andA fifty micro-second gate 21 which is applied toV coincidence circuit No. 3, identified by the numeral 2,2, where the third positive oscillator pulse is selected (T equals seventeen `'hundred fifty micro-seconds). This third osillator pulse and the trigger pulse are fed to mixer No.

. 3 identified by the numeral 12. The three mixers produceno output until theb'u/ttons orks'witches 1, 2, or V3 are closed to operate the control relays inthe mixer circuits. By the means l-just described, the operation of button -1 will produce output pulses separated by fifty micro-seconds (to interrogate or trigger airplane No. 1), the operation of button 2 will produce output pulses separated by one hundred and fifty micro-seconds (to interregate lor trigger'airplane No. 2), and the operation of button 3 will produce output pulses separated by two hnd'rd andfiftyv micro-seconds (to inter-regate or trigger'airplane No. 3*). Only one airplane is interrogated at Va time. i

In following the aforesaid description, reference to Fig. 2 andthe wave forms shown therein, will'be helpful.

The Eccles-Jordan circuit 15 generates a pulse which is coincident with the second of the interrogation pulses '(T eq'uals fifteen hundred fifty micro-seconds) and which serves 'as the, timing pulse to initiate the operation of the command pulse generator.

Codercommand pulse' generator The command pulse generator, known as the 'Command Unit in Fig. 1, generates the command or control pulses which are timed with respect to the second of the two -int'eri'ogating pulses. V,

To describe the operation of the Command Unit,'it will "be assumed that airplane No. 1 is being interrogated and therefore the input timing'pulse from the vSynchronizing Unit occurs at T equals 'fifteen hundred fifty micro'- 'secon'ds Now having reference to Figs. 1 and 3, partic- .ularly the latter, the timing pulsestarts a two hundred 'fiftymicrolsecond delayed gate, identified in the block wiring diagram by the numeral 23, whose trailing edge` occurs at T equals eighteen hundred micro-seconds, and the output of the gate is used to trigger a four hundred micro=second 'gate 2'4 and a one hundred micro-second gate 25. The four hundred lmicro-second gate 24 shockexcites -a ten kc. oscillator 26 whose output issquared and differentiated at Y27 to produce a-signal of alternately positive and negative pulses fty micro-seconds apart and starting with a negative pulse at T equals eighteen hundred micro-seconds. This signal goes to coincidence 'circuit Nos. 1, 2., 3 and 4, and identified respectively,-by the numerals 28, 29, 30 and 31. ,y Y

The one hundred micro-second gate 25, starting at T equals eighteen hundred micro-seconds and ending at T equals nineteen hundred micro-seconds, is applied to' coincidence ycircuit No. 1 (block diagram 28) and allows the first lpositive oscillator pulse to produce an output pulse at AT equals eighteen hundred fifty micro-seconds which is applied to mixer No. 1j, block diagram 3-2, Vand to mixerNo. 3, block diagram 33. Also, the Vfirst positive oscillator pulse at T equals eighteen hundred fifty micro-seconds is applied to and triggers a one hundred and fifty micro-second gate, identified in the'blocky diagram by the numeral 34. The one hundredA and fty micro-second .gate 34 starts at `T equals `eighteen hundred and ft'y micro-seconds and ends at T equals two Vthousand micro-seconds, and is-applied to coincidence .circuit-No. 2 (block diagram 29) to allow the second positive oscillator pulse to produce an output pulse at T lequals nineteen hundred fifty micro-,seconds Ywhich is applied-'to mixer No. 1 (block diagram 32) and to mixer NQ.A 2 (identified as block diagram number 35.).

. Thegsecondfpositive oscillator pulse producing an outalso applied to and triggers ajsecondone hundred and fifty micro-second gate, identified in the block diagram bynumeral 36; Gate 36 starts at T equals nineteen hundred fifty micro-seconds and ends at T` equals twenty one hundred micro-seconds, and is applied to coincidence circuit No. 3 (block diagram 30) to allow the third positive Y"oscillator pulse to produce an output pulse at T equals twenty Vhundred Aand fifty micro-seconds,` which -is applied to mixer No. 2 (block diagram 35), and mixer No. 3 (block diagram 33),- and which also triggers a one hundred and fifty micro-second .gate No. 3, and identied by the numeral 37 in the block'diagram. Gate No. 3 (block diagram 37.) starts --at T equals twenty hundred and fty micro-seconds and ends at T equals twenty-two hundred micro-seconds and is -applied to coincidence circuit -No, 4 (blockdiagram 3l) to allow the fourth positive oseillator pulse to producey an output pulse at equals twenty-one hundred and fifty micro-seconds which is applied to` mixer No. 4, identified in the block diagram by numeral 38, and which also triggers a phantastron gate 39. Each one ofthe gates 34, -36 and 37 has rounded corners (see Fig. 3) to prevent the initiating pulse ,from appearing at the output.V

When the .le'ft control 4 is energized, the output of nixer No. l (identified in block diagram by the number' 32), consisting of two pulses T equals eighteen hundred vfifty micro-seconds and T equals nine hundred and fifty micro-seconds, goes through mixer No. 5 (block diagram 40), to the output modulator *lead 41 which will impart to the radar wave the aforesaid two pulses atY the indicated tine. When the right command control 5 yis energized, the output of mixer No. 2 (block diagram 35), 'consisting of two pulses T equals nineteen hundred and fifty micro-seconds and T equals twenty hundred and nffy micro-seconds, goes 'through mixer No. 5 (block diagram 40)"'to the modulator lead 41. In a like mant ner,- when the down command control-6 is energized, the output of mixer No. 3 (block diagram 33) goesthrough mixer No. y5 (block diagram 40) to the 'modullatr lea'd`41. The leftf right, and down command relays are so connected as to prevent more than 'one "relay being energizedat one time.

When a single vfixed pulse is desired for the fourth jcomrlnand, the variable gate 39 is inoperative and the onlyinput to mixer No. 4V (block diagram y38.) is a single pulse from coincidence circuit No. 4 v(blockY diagram 31) occurring at equals 'twenty one hundred fifty micro-secponds.- Whenthe variable control command'is desired, -the gate 39.islrendered operative by `positioning potentiometer-Tand' is `triggeredfby the fixed pulse just lfitnenticztrl'edV The .vai'iablefgatef39 output is apulse Aoccurrin-g.`between T equals twenty-one hundred fifty micro- Aseconds and Tequalsvtwenty-two ihundred iiftyimicro-seconds and-afterampliticatiorrby the -pip amplifier 42 fis applied to mixer No.7*4 (block 'f'l-iagram). The output .ofmixer No.4 iin 'either fixed (single pulse) or variable (double pulse) form .goes through'mixer No. 5 (block ldiagijam 40.) to thefoutput modulator .lead 41.' rThis fourth command auxiliary maybe sent simultaneously with -any one of the other three'commands.

. Decoder-,general description The decoder, shown in block diagram'form `in -Fi`g."=4, is associated with ,the receiver in theremotelyfcontroliled a'hefand includes an interrogation 'Spulse vanalyzer or hnizing Unit and .a command pulse analyzer V6r 4 and "IniFi/g. 4, a'dash-linethroughithe bleek grain 4separates the SynchrfonizringY Unit Vfrom'fthe Comn 'dUr'ijiLd Tlredecoderequipment 'analyzesthe receiver i lo'u'tput fand "the Vinterrlo'gati'ng. o r 'synchronizing nsignals areV correct, then 'extactsjfhe pulses pertaining to the mamans-intelligence whiniwas transmittedbverean cycle of the radar .wave9btween Tequals iifteenhndrd Putpulse at nineteen jhundred and fifty Jlient-seconds iis T .and tlf equals twentyfwhundre litire-Secsndrenl-P @censos vides signal output of. each `command function for control '0f the auto pilot and course corrector. A

The output of the airplane receiver is fed to the decoder which not only actuates the proper control channels as aforesaid, but which also activates a beacon transmitter carried by the airplane so as to permit beacon response tothe received radar search pulse. The use of a beacon transmitter and the beacon response make it much easier to follow the airplane at a considerable distance than if the radar echo alone were relied on. HIt will be understood that the beacon transmitter operated by the airplane will be actuated within the limits between T equals zero and T equals fifteen hundred micro-seconds of each radar wave cycle. The first cycle that will `be accepted in one search pulse or radar cycle, is the interrogation signal consisting Yof, two [pulses with a time spacing predeterminedfor a given remotely controlled airplane and the decoding apparatus associated with the radio receiver thereof. When thesignal is received and accepted, the decoder command "signal analyzer, or Command Unit, is energized and the subsequent control signal pulses are analyzed. This se- Aquence must be completed in one Search pulse or radar cycle, i.e.,.T equals zero to T equals twenty-live hundred micro-seconds.

The outputs of the decoder for` the left, right, and down functions are in the form of three separate D.C. voltages which are utilizedby a course corrector system in conjunction with the airplanes automatic pilot. The output of the fourth function auxiliary may be either a single narrow pulse or a wide pulse (gate) whosegwidth varies according to the proportion of the control desired for the controlled aircraft, as explained in part in conjunction with the Command Unit of the coder apparatus.

Decoder--interrogaton pulse analyzer The interrogation pulse analyzer, that is, the Synchronizing Unit in Fig. 4, analyzes the receiver output of the airplane and selects the proper interrogation signal if it is present. When such an interrogating signal is received and accepted by the Synchronizing Unit, this unit provides a pulse to the Command Unit to initiate its operation.

The signal output of the airplane receiver 43, consisting of positive pulses, is passed to the synchronizing Unit of the decoder, where it is applied to a bias amplifier 44 whose output will contain the peaks of the signal pulses and very little of the receiver noise. The signal from the amplifier 44 is applied to a variable or selector gate cir- 'cuit 45 which may be triggered by any one of the incoming pulses. However, it will be apparent from a study of the wave forms (see Fig. that the` synchronizing Unit of the decoder will only produce an output to the Command Unit when the variable gate 45 starts with the `iirst of the synchronizing pulses, marked Sync-A in Fig. 5.

The variable gate 45 is controlled by switch mechanism 46, the switch mechanism being adapted to be set at either station Nos. 1, 2, or 3, it being understood that in airplane No. l Vthe switch mechanism 46 will be set at station No. l, in airplane No. 2 at station No. 2, and in airplane No. 3 at station No. 3, to thereby set the gates 45 on the decoding apparatus of the several airplanes so that each gate will be different from the other to insure response or acceptance of interrogation signals only when intended for the specific airplane.

From the variable gate 45 the received pulses pass to Ya biased amplier 47 and thence to a blocking oscillator 48. For airplane No. 1, the blocking oscillator will pro- ,duce an output pulseon the rst input pulse occurring at .T equals fteen hundred` twenty-tive micro-seconds, for airplane No. 2, an output pulse occurring `at T equals sixteen hundred and twenty-tive micro-seconds, and for `airplane No. 3, an output pulse occurring at T equals seven- ,teen hundred and twenty-live micro-seconds.

To describer the operation further, it is assumed at this `point that the variable gate 45 is setter airplane No. 1,

and thus the blocking oscillator produces an output pulse at fteenhundred twenty-live micro-seconds. This pulse triggers a fty micro-second gate 49 which is applied to coincidence circuit 50 and which will allow the coincidence circuit to .lire if there is a pulse onthe incoming signal .which lies between T equals iifteen hundred twentytive micro-seconds and T equals iifteen hundred and seventy-live micro-seconds, as applied thereto from the biased amplifier 44. `If airplane No. 1 is being interrogated the Sync-B pulse (see Fig. 5) occurring at T equals fteen .hundred fifty micro-seconds coincides with the gate and will produce an output pulse fifteen hundred and fifty micro-seconds which is the timing pulse for the command unit.

Decodercommand pulse analyzer The command pulse analyzer, or Command Unit in Fig. 4, is placed in operation by the timing pulse derived from the synchronizing Unit as just described, with the Command Unit then analyzing the command signal pulses. Such action is completed during one search pulse or radar cycle (T equals zero to T equals twenty-five hundred micro-seconds). The wave forms are shown in Fig. 5.

To facilitate description of the operation, it is assumed that the synchronizing times of airplane No. l are set up in the interrogation pulse analyzer. The timing pulse from the Synchronizing Unit, at T equals lifteen hundred ifty micro-seconds under this condition, triggers a two hundred and fifty micro-second gate circuit 51 used as a fixed delay. The trailing edge of this gate (at T equals eighteen hundred micro-seconds), triggers a four hundred microsecond gate 52 which shockexcites a twenty kc. oscillator 53 whose rst half cycle of oscillation is negative.

The oscillator output is squared and differentiated' at 54, and is applied to a biased ampler 55 to clip oi the negative pulses, The amplifier output is a series of eight positive pulses, fifty micro-seconds apart and starting at T equals eighteen hundred and twenty-tive micro-seconds, and the output of the cathode follower 55 is passed to seven Eccles-Jordan circuits, indicated respectively by the numerals56 to 62. The output of Eccles-Jordan circuit 57 extends `to a cathode `follower 63, the output of Eccles-Jordan circuit 59 extends to a cathode follower 64, the output of Eccles-Jordan circuit 61 extends to a cathode follower 65, and the ouput of Eccles-Jordan circuit 62` extendsto a one hundred twenty-live microsecond gate 66. Cathode follower '63 connects to coincidence circuit 67, cathode follower 64 connects to coincidence circuit 68, cathode follower 65 connects to coincidence circuit 69, and gate 66 connects to coincidence circuit 70. Coincidence circuits 67, 68, 69 and 70 are all connected to the biased amplifier 44.

The output pulse of coincidence circuit No. l (block `diagram 67) triggers` a two hundred and tifty microsecond gate 71 which starts at T equals eighteen hundred and fifty micro-seconds and ends at T equals twentyone hundred micro-seconds. This gate is applied to coincidence circuit Nos. 5 and 6, identified in the block diagram by numbers 72 and 73, and will allow passage of `the pulses from coincidence circuits Nos. 2 and 3. The output of coincidence circuit No. 5 will then be a fsingle pulse at T equals nineteen hundred and fifty microseconds, and occurring only when the left command is produced by the coder. The output of coincidence circuit No. 6 will be a single pulse at T equals twenty hundred and fifty microseconds, and occurring only when the down command is produced by the decoder. The output pulse of, coincidence circuit No. 2 also triggers a one hundred and fifty micro-second gate (block diagram 74) whichstarts at T equals nineteen hundred and fifty micro-seconds and ends at T equals twenty-one 'hundred micro-seconds. This gate is applied to coincidence circuit No. 7 (block diagram 75) and will allow 9 passage` of the pulsejfrom coincidence circuitV No'.I 3:- Thev output of coincidence circuit -No7 willgthn be a singlel pulseat T equals twenty hundred and fifty microfsecon'd's',- and Aoccurring on-lywhen the fright command is rproduced bythe gwcoder. The right, leftf and down pulses are fed to the signal control circuits, indicated-respe'ctively by the numerals 76, 77, and 78, to produce D.C. control voltages for the course corrector f theauto pilot. A f t Having reference to Fig. 6; th'e fl'eft, and righ signal control circuits are actuated by the :signals described above which trigger the'fthyratrons' T1 and shown. Relay K`1,Yenergized by D. C. voltage from the course correction-is Vnornalfy cldsdpvi'dinfgliplate voltage for bothgT1 and,'-1`2gthrough relays K2 and K3. If

111e second `,ser or contacts on 51g? grounds tnegjpiat 1 ,to jnirn n 'on 'and at' the sante time hold K2 The` auxiliary `VA itrol is obtaiieydr'in the following i'ralrini: The `t of tlie 'drie hinvdred twenty-nyc inici'cs'coiid gt `66 applied to 'cincideiicle'cirit No. 4 (block diagram 70) and allows passage of the No. 49 command pulse (see Fig. 5) at T equals twentyone hundred fifty micro-seconds, and also the No. 4b command pulse which may occur between T equals twenty-one hundred fifty micro-seconds and T equals twenty-two hundred and fifty micro-seconds. If the system is pre-set Vfor xed control by a switch 79, the output of coincidence circuit No. 4 will be a single pulse at T equals twenty-one hundred fifty micro-seconds which goes through a cathode follower 80 to an output jack 81. If the variable control is used, the No. 4a and No. 4b output pulses of coincidence circuit No. 4 are applied to the Eccles-Jordan circuit 82 whose output will be a gate starting with the No. 4a pulse and ending with No. 4b pulse. This gate comes to van output jack 83.

The trailing edge of the one hundred twenty-five microsecond gate 66 is used to trigger a four hundred microsecond gate 84. This gate is applied to the radar coincidence circuit 85 as is the biased amplifier 44, to allow the radar-search pulse at T equals zero micro-seconds to trigger the beacon transmitter 86. This trigger pulse at T equals zero micro-seconds is also applied to the Eccles-Jordan circuit 82 to insure proper operation of this circuit during the following command period of the radar cycle.

From the foregoing, it will be recognized that the various objects of the invention have been achieved by the provision of interrogating and command apparatus in association with a radar-transmitter, together with interrogation responsive and command responsive apparatus in conjunction with one or more airplanes or other bodies being remotely controlled, whereby the radar will not only serve to follow the remotely controlled airplanes or other bodies, but will also function to control them. In addition, the radar may simultaneously function to locate target, landing, or other items or areas. Three or more airplanes or other bodies can be followed and controlled, although it is to be understood that the apparatus may be utilized in conjunction with the control of a single airplane or other body. If this be the case, part or all of the interrogation or synchroi natedt; Theapparatus has been `ilh'istratteda'nd described as including three on-oftypes of command, plu'sa` fourth' xed or variable control. Theexact numberr'and the'particular type of commands can obviously be-altered `is dnd in th appended claims.

The terms radar apparatus, rada'r transmitter, or radar as `vemployed inthe specification and rclaims are intended to define what m'ight be termed a conventional radar system including an ultra 'high frequency transmitte'r operating into a narrow beam antenna which is swept in scanning movement of periodic repeated character, togethefr with a reeivr for receiving th'e radar echoes or reflected signals; The transmitter operates to repeat its fractional micro second radar search pulse at intervals of several `thousand micro seconds` so that some fo'ur hundred search pulse cycles Yper second are achieved.

n1. Remote control apparatus Ycor'nprising a radar transmitter and ech receiver, afcoder'includin'g a synchronizing'unit for modulating the transmitted radar wave with f any 'selected' set of 'a plurality of`sets of differently timeseparatedv pulses, a decoder carried by lthe body 'bein'g controlled, and including 'a synchronizing unit responding to nly'one 'selected set of time-separated pulses', a cinmand'initiin the; cod'e'rfor modulating thtransmit: ted radar wave with any selected set of a plurality of sets of differently time-separated pulses, a command unit in the decoder responding to any selected command accepted by the synchronizing unit of the decoder for establishing electric current llow to operate controls on the body, and a beacon transmitter triggered by the decoder for transmitting a beacon signal to the radar echo receiver.

2. Remote control apparatus comprising a radar transmitter and echo receiver, a coder including a synchronizing unit for modulating the transmitted radar wave with any selected set of a plurality of sets of ditferently timeseparated pulses, a decoder carriedr by the body being controlled and including a synchronizing unit responding to only one selected set of time-separated pulses, `a command unit in the coder for modulating the transmitted radar wave with any selected set of a plurality of sets of differently time-separated pulses, and a command unit in the decoder responding to any selected command accepted by the synchronizing unit of the decoder for establishing electric current flow to operate controls on the body.

3. In combination in apparatus for following and controlling a body, a radar apparatus having a search pulse cycle approximately twice as long as thetime required to return the last desired echo signal, means for modulating the radar wave at a specific time after the start of the search pulse cycle and after the return of the lust desired echo signal to provide a irst set of a plurality of pulses separated by coded time intervals, switch means for changing the coded selection of the specific time of operation of the radar wave modulating means, means carried by the body being controlled for picking up they pulses, selector gate means for accepting the interrogating pulses if properly coded as to time, means triggered by the acceptance of the pulses for establishing command channels and for supplying control currents to the body, means modulating the radar wave to produce a second set of pulses separated by coded time intervals through the command channels to control the operation of the control currents, and means triggered by the acceptance of the first set of pulses for transmitting a beacon signal knizing apparatus of the coder and decoder may be elimto the radar echo receiver.

1 1 4; In combination in apparatus foffollowng and'conl' trolling a body, a radar apparatushaving a search -pulse cycle approximately twice'as long'as the `time required to return the last desired echo signal, meansincluding selective switch mechanism for modulating the radar Wave at a selected time after the start of the search pulse cycle and after the return of the last desired echo signal to provide a set of pulses of a selected time separation, means carried by the body being controlldfor picking up the time coded pulses, selector gate means'for accepting or rejecting the interrogating pulses, and means triggered by the acceptance of the pulses for establishing control channels in the body, means for modulating the radar wave at a selected time interval after the `first set of pulses to provide a second set of pulses ofselected time separation for controlling the supply of control currents to the body through the control channels of the body pulses. a; 5. In combination in apparatus for following abody, a radar apparatus, means for modulating the radar wave at a specicbut selectively variable time aftethe'start of the search pulse cycle and after the return of thetlast desired echo signal to provide time separated-pulses `3f time coded interrogating character, m'eans carried bythe body being controlled for picking upthe interrogating pulses, a time coded selector gate circuit for accepting or rejecting the interrogating pulses,and means triggered-by the acceptance of the interrogating pulses for transmit-V ting a beacon signal to the radar e'cho receiver.` A 6. In combination in apparatusfor following and con trolling a plurality of bodies, a radarapparatus having `a search pulse cycle approximately twiceas long as the pulses for establishing command circuits and for supply'- ing control currents to the body.`

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